There’s plenty of vacant office space south of Seneca Street in Seattle’s central-business district, and there will be more soon.

Bank of America, which at one point in the 1990s was downtown’s biggest office tenant and had naming rights to Columbia Center, will be giving back a big chunk of space at Fifth Avenue Plaza.

A Bank of America spokeswoman said the bank is reducing its occupancy at 800 Fifth Ave. starting in January. Until now, the 934,000-square-foot building, which is owned by Houston-based Hines, has had little vacancy.

The bank leases about 780,000 square feet under a 35-year deal that expires in 2016. Of that amount, the bank subleases 270,000 square feet and occupies 510,000 square feet, a spokeswoman said.

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While Bank of America won’t say how much space it’s vacating, people familiar with the matter said it was roughly 300,000 square feet, leaving a footprint of about 200,000 square feet.

It’s another blow to Seattle’s downtown, which has a vacancy rate hovering near 15 percent if available subleases are counted, according to OfficeSpace.com.

Brokers say the lingering high vacancy rate in Seattle’s downtown can be traced to the failure five years ago of Washington Mutual.

The Seattle-based thrift was downtown’s largest office tenant when federal regulators seized it in September 2008 and sold most of its assets to JPMorgan Chase, which was allowed to break WaMu’s leases without penalty.

WaMu vacated 288,000 square feet it leased in 1111 Third Ave., or half of the tower’s office space; the building’s vacancy rate is still 54 percent, according to Office-Space.com.

And 1201 Third Ave., once known as the Washington Mutual Tower, is 20 percent vacant, Office-Space.com reports.

With Bank of America’s impending giveback of space, downtown “still has a long way to go to get back to where we were,” said Jesse Ottele, senior vice president at CBRE in Seattle.

The state says there were 16,400 jobs in banks and brokerages in King County in August, the latest period available, down 28 percent from the same period five years ago.

Even so, there are bright spots as surviving banks renew or expand their space:

• U.S. Bank recently renewed its lease at U.S. Bank Centre for 120,000 square feet.

• Wells Fargo leases about 250,000 square feet, which is 27 percent more than it did in 2008.

Bill Pollard, managing principal of Talon Private Capital, said more than $10 million has been invested in 1111 Third Ave. to make it more attractive to tech firms.

“We’re going to go out and poach demand from others,” Pollard said.

Mercer Island a pricey market

If you own a four-bedroom home on Mercer Island, you’ve made Coldwell Banker’s top 25 list of most expensive markets nationwide in 2013.

The real-estate brokerage ranked Mercer Island 21st with an average listing price of $999,276.

Coldwell Banker Real Estate produces the annual ranking of more than 1,900 markets by analyzing listings in the brokerage’s network for four-bedroom, two-bath homes for sale between January and June. The brokerage says this method offers an apples-to-apples comparison across markets.

It’s no surprise that places in California made up nearly half of the top 25 markets. Within Washington state, Bellevue, Newcastle, Seattle and Woodinville round out the top five markets here with the highest average price — all exceed $650,000 — for that type of home.

For those looking for a four-bedroom home, the Seattle-area cities with the lowest average list prices in Coldwell Banker’s rankings were Auburn ($273,512), Kent ($313,013) and Lynnwood ($331,686).

One important caveat: The study excluded markets with fewer than 10 listings for four-bedroom, two-bath homes. That eliminated San Juan County, one of Washington state’s most expensive housing markets.